Vitamin A is found as Retninol or performed vit.A from animal sources or Carotenoids or provitamin A from plant source beta-carotene.Current recommended upper limits pof Vit A daily intake range from 1,500 mcg(for supplement intake alone) to 3,000mcg (for dietary and supplement intake combined).The EU RDA is 800mcg of retinol equivalent.
These are unlikely since it is stored in the liver and lasts months. Pregnant women should avoid retinol, to prevent excess storage in the unborn baby's liver. Natural beta carotene is safe in pregnancy since it is only converted to vitamin A in the liver and intestine as and when the body requires it. As the quantity of Beta Carotene increases, the proportion of the absorbed material converted to Vitamin A decreases and more of the carotene enters the bloodstream unchanged. In some conditions, this is a desirable state of affairs for two main reasons; (i) toxic amounts of Vitamin A will not be produced even when Beta Carotene is high and (ii) Beta Carotene is regarded as non-toxic even when taken in quantities sufficient to impart a yellow colouration of the skin.
Coeliac disease, cystic fibrosis, chronic liver disease and chronic pancreatitis might cause secondary deficiency. Night blindness; xerophthalmia; keratomalacia; increased morbidity and mortality in childhood.
A recent study published in the New England Journal of Medicine involving 2,322 Swedish men indicates that too much Vitamin A can lead to increase in fracture risk http://content.nejm.org/cgi/content/short/348/4/287. Patients with well established osteoporosis should watch there intake especially if taking cod liver oil where fish body oil would be a better substitute.
Vitamin A is essential for a healthy immune system, eyes ( Photoreceptor mechanism of the retina); ( epithelial integrity); lysosome stability; glycoprotein synthesis ;skin, hair and nail health; It maintains the mucous membranes of the respiratory, digestive and urinary tract .Beta Carotene is stored in the fatty tissues of the body and circulates in the bloodstream, where it has been found to be a potent anti-oxidant and free radical scavenger. A recent research paper in the Lancet (2003:361:207) suggests the use of vitamin A in supplements should be 'actively discouraged' because it can contribute to an increase in cardiovacular death and all cause mortality.
Lamberts Natural Beta Carotene is extracted in the
natural form from Dunaliella salina, a pink alga which lives
on the surface of salt lakes and which contains small
amounts of other, mixed carotenoids. The growth of the
organism is controlled in a high salt water environment
which precludes contamination by harmful micro-organisms.